Pressure actuated fuel injection system for free-piston engines



Sept, 13, 1949.

Filed June 10, 1947 2 Sheets-Sheet 1 #3 Q Q Qt mil/1W ATTORNEY p 1949-R. J. HOOKER 2,481,927

I PRESSURE ACTUATED L INJECTION SYSTEM FOR FREE-P O ENGINES Filed June10, 1947 2 Sheets-Sheet 2 INVENTOR Hai a)? eZHooke r ATTORNEY PatentedSept. 13, 1949 PRESSURE ACTUATED FUEL INJECTION SYSTEM FOR FREE-PISTONENGINES Ralph J. Hooker, Hamilton, Ohio, assignor to United AircraftCorporation, East Hartford, Coma, a corporation of Delaware ApplicationJune 10, 1947, Serial No. 753,642

13 Claims.

i This invention relates to a pressure actuated fuel injection systemparticularly adapted for free-piston units.

in compression ignition engines, it is advantageous in many cases tohave the fuel injected at a predetermined compression pressure. This hasbeen accomplished by arranging the fuel injection device so that theflow of fuel into the engine cylinder will take place under the controlof a valve which is responsive to pressure within the engine cylinder. Afeature of this invention is the actuation of the pump plunger bypressure from the engine cylinder. feature is the arrangement of thedevice, such that the injection plunger is moved rapidly on theinjection strolze when the predetermined compression pressure isreached.

Free-piston generally have air springs which function to move the enginepistons on the compression stroke. These air springs may he a part ofthe compressor elements or may he separate air springs. In either eventthe air pressure in the air spring is highest at the end of the powerstroke of the engine piston at which time the pressure in the enginecylinder is at a minimum. A feature oi this invention is the use ofpressure as from the air spring for returning the injection plunger onthe filling stroire. It will be understood that instead of air springpressure, the pressure within the compressor cylfinder might he used.

A icature oi the invention is an arrangement for adjusting the quantityof incl i'or each stroke oi the plunger by limiting the plunger stroke.

Other objects and advantages will be apparent irom the specification andclaims and from the accompanying drawings which illustrate an emhodimentoi the invention.

i is a sectional view of the free-piston unit showing the injection pumpin elevation.

2 is a sectional view on a larger scale oi the injection device.

The unit shown includes an engine cylinder it having reciprocatingpistons :12 and it to which compressor pistons it and it in cylinders itand it are integrally connected. Sleeves it and 26 attached to thecompressor pistons complete the reciprocating piston assembly. Thesleeves in conjunction with stationary pistons 2t and 3t form air springcylinders.

The pistons are moved apart by the burning of iuel injected into enginecylinder it through a fuel nozzle 32, Fig. 2. Air compressed in the airspring cylinders on the power stroke returns the piston assemblies onthe compression stroke.

Another 2 The pistons are always maintained at equal distances from thecenter of the engine cylinder by a linkage, not shown.

The intake manifold 38 which extends around the compressor and enginecylinders conducts air to intake valves 40 in the heads of thecompressor cylinders through which air automatically enters the oppositeends of the cylinders. Compressed air leaves the cylinders throughdischarge valves 42, also at opposite ends of the compressor cylindersand passes into a central scavenge cham-= ber i l and end chambers itand 38. These chambers may be connected by a scavenge manifold, notshown.

Compressed air from the scavenge chambers enters engine ports til whichare uncovered by piston it at the end of the power stroke, therebypermitting air to be blown through the engine cylinder. Gas in theengine cylinder is discharged through exhaust ports 52 uncovered by thepiston t2 and into an exhaust manifold it.

The fuel for the nozzle 32 is supplied by a fuel injection device whichis actuated on the injection stroke by a compression pressure and whichis returned on the pumping stroke by air from one of the air springs. Asshown in Fig. 2, the injection device includes a casing tit having afuel inlet 58. Within the casing is a cylinder tit having a bore inwhich the injection plunger til reciprocates. The cylinder has an inletpassage til, the inner end of which is covered by the plunger on theinjection stroke, thereby trapping fuel in the end of the hore tit andforcing it out past a check valve fit and through the nozzle 32. Thelatter may be held in place 'by a ring it which also functions to holdthe cylinder Ed in position.

The plunger extends beyond the cylinder til at its outer end and engageswith a disc 322 which is moved outwardly by a spring it, thereby holdingthe end of the plunger against the rod it of a piston it. The piston itis slidable in a casing til and has a projecting valve element 82 whichcloses an inlet passage M in the casing which is connected, as by a pipeto, with the engine cylinder. When the pressure in passage 8t is highenough to overcome the action of the spring it, the piston it movesupwardly,

allowing the compression pressure from the engine cylinder to beefiective overthe entire area of the piston and cause rapid upwardmovement of the piston and corresponding movement of the injectionplunger to deliver fuel to the engine cylinder.

The other side of the piston it is acted upon by pressure from one ofthe air springs through a duct 88 and a passage 90 in a plate 92 betweenthe outer end of the casing 56 and the end of the casing 80. As thepistons reach the outer ends of their strokes so that the enginecylinder pressure drops to that of the pressure in the scavengemanifolds, the air spring pressure will be high enough to return thepiston I8 to the position shown, thereby causing the injection plungerto return to the position shown under the action of the spring I4.

For limiting the quantity of fuel injected on each stroke. the casing 56supports a ring 94 having teeth 95 on its outer surface engageable witha rack 96 slidable in the casing. The inner surface of the ring 94 hassplines 98 engaging with the outer surface of a sleeve I which hasthreads cooperating with similar threads I02 on the cylinder 60.Movement of the rack 96, one end of which extends beyond the casing 56,thus turns the sleeve I00 on the cylinder and adjusts the verticalposition of the lower end of the sleeve, thereby limiting the plungerstroke since the disc 12 engages with the end of the sleeve.

For the purpose of adjusting the time of injection, the tension ofspring I4 may be changed as by substituting a different spring. Analternative adjustment may be efiected by providing a ring I02 in thecasing 56 surrounding and in threaded engagement with the periphery ofthe plate I04 against which the spring I4 rests. When the ring I02 isturned as by a rack I06 engaging teeth I08 on the ring, the plate I04will be moved downwardly to increase the tension of the spring. A pinIIO may hold the plate against turning. Obviously the actuation of rackI06 may be manual or automatic, as desired.

In operation, with the parts in the position shown, the engine pistonsare moved toward each other to build up a pressure in the enginecylinder for the purpose of igniting the fuel to be injected therein.When this compression pressure reaches a predetermined value, which is afunction of the area of the passage 84, and the strength of spring I4,the piston 10 is moved rapidly upward, thereby moving the plunger 62upwardly, first closing the inlet passage 64 and then forcing fuel pastthe check valve and through the fuel nozzle into the engine cylinder.This causes combustion to take place in the engine cylinder, and thepistons move apart, thereby building up a pressure in the air springs.When the exhaust ports are uncovered causing a substantial drop in thepressure in the engine cylinder, air spring pressure is acting on theupper side of the piston 1-0 returning it to the position shown, therebycausing the return of the injection plunger to the position shown sothat the space 66 may again be filled with fuel in readiness for thenext injection.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaims.

Iclaim:

1. A free-piston unit including opposed piston assemblies includingengine and compressor pistons, an engine cylinder in which the enginepistons are positioned, compressor cylinders at the ends of the enginecylinder for the compressor pistons, and air springs acting on eachpiston assembly for moving the assemblies toward each other on thecompression stroke, in combination with an injection device fordelivering fuel to the engine cylinder, said device including a housinghaving a bore and an inlet port to said bore, a plunger reciprocating insaid bore, and a nozzle through which fuel entering said inlet isdelivered to the engine cylinder, and means responsive to pressurein theengine cylinder for moving the plunger on the injection stroke 2. Afree-piston unit including opposed piston assemblies including engineand compressor pistons, an engine cylinder in which the engine pistonsare positioned, compressor cylinders at the ends of the engine cylinderfor the compressor pistons, and air springs acting on each pistonassembly for moving the assemblies toward each other on the compressionstroke, in combination with an injection device for delivering fuel tothe engine cylinder, said device including a housing having a bore andan inlet port to said bore, a plunger reciprocating in said bore, and anozzle through which fuel entering said inlet is delivered to the enginecylinder, means responsive to pressure in the engine cylinder for movingthe plunger on the injection stroke, and other means for causing theplunger to move in the opposite direction on the filling stroke inresponse to pressure in the air spring.

3. A free-piston unit including opposed piston assemblies includingengine and compressor pistons, an engine cylinder in which the enginepistons are positioned, compressor cylinders at the ends of the enginecylinder for the compressor pistons, and air springs acting on eachpiston assembly for moving the assemblies toward each other on thecompression stroke, in combination with an injection device fordelivering fuel to the engine cylinder, said device including a housinghaving a bore and an inlet port to said bore, a plunger reciprocating insaid bore, and a nozzle through which fuel entering said inlet isdelivered to the engine cylinder, means responsive to pressure in theengine cylinder for moving the plunger on the injection stroke, andmeans for limiting the stroke of the plunger for controlling the fuelquantity delivered on each stroke.

4. A free-piston unit including opposed piston assemblies includingengine and compressor pistons, an engine cylinder in which the enginepistons are positioned, compressor cylinders at the ends of the enginecylinder for the compressor pistons, and air springs acting on eachpiston assembly for moving the assemblies toward each other on thecompression stroke, in combination with an injection device fordelivering fuel to the engine cylinder, said device including a housinghaving a bore and an inlet port to said bore, a plunger reciprocating insaid bore, and a nozzle through which fuel entering said inlet isdelivered to the engine cylinder, means responsive to pressure in theengine cylinder for moving the plunger on the injection stroke, meansfor limiting the stroke of the plunger for controlling the fuel quantitydelivered on each stroke, and other means responsive to pressure in theair spring for causing the plunger to move on the filling stroke.

5. A free-piston unit including an engine cylinder and piston, acompressor cylinder and piston, said cylinders being connected togetherand said pistons being interconnected to reciprocate as a unit in saidcylinders, an air spring including piston and cylinder elements, one ofwhich is connected to the pistons to move therewith, said air springcausing movement of the pistons on the engine compression stroke, incombination with an injection device for delivering fuel to the enginecylinder including a fuel injection pump, means for actuating the pumpfor the delivery of fuel to the engine cylinder in response to pressurein the engine cylinder, and means for causing the pump to move on thefilling stroke in response to pressure in the air spring.

6. A tree-piston unit including an engine cylinder and piston, acompressor cylinder and piston, said cylinders being connected togetherand said pistons being interconnected to reciprocate as a unit in saidcylinders, an air spring including piston and cylinder elements, one ofwhich is connected to the pistons to move therewith, said air springcausing movement of the pistons on the engine compression stroke, incombination with a fuel injection device for delivering fuel to theengine cylinder including a housing having a bore and an injectionplunger reciprocating in said bore, a passage from said bore to theengine cylinder and an inlet passage for fuel to enter said bore, aspring acting on said plunger to move it in one direction, andpressure-actuated means for moving the plunger in the oppositedirection, said pressure-actuated means being connected to the enginecylinder.

7. A free-piston unit including an engine cylinder and piston, acompressor cylinder and piston, said cylinders being connected togetherand said pistons being interconnected to reciprocate as a unit in saidcylinders, an air spring including piston and cylinder elements, one ofwhich is connected to the pistons to move therewith, said air springcausing movement of the pistons on the engine compression stroke, incombination with a fuel injection device :lor delivering fuel to theengine cylinder including a housing having a bore and an injectionplunger reciprocating in said here, a passage irorn said bore to theengine cylinder and an inlet passage for fuel to enter said bore, aspring acting on said plunger to move it in one direction, andpressure-actuated means for moving the plunger in the oppositedirection, said last means including a piston, a cylinder in which saidpiston reciprocates, and a valve element substantially smaller in areathan the piston connected thereto, said valve element closing anadmission port to the last-mentioned cylinder.

3. A iree piston unit including an engine cylinder and piston, acompressor cylinder and piston, said cylinders being connected togetherand said pistons being interconnected to reciprocate as a unit in saidcylinders, an air sprin including piston and cylinder elements, one ofwhich is connected to the pistons to move therewith, said air springcausing movement of the pistons on the engine compression stroke, incombination with a fuel injection device for delivering fuel to theengine cylinder including a housing having a bore and an injectionplunger reciprocating in said here, a passage from said bore to theengine cylinder and an inlet passage for fuel to enter said here, aspring acting on said plunger to move it in one direction, andpressure-actuated means for moving the plunger in the oppositedirection, said last means including a piston, a cylinder in which saidpiston reciprocates, and a valve element substantially smaller in areathan the piston connected thereto, said valve element closing anadmission port to the last-mentioned cylinder, said admission portcommunicating with the engine cylinder. 4

9. A free-piston unit including an engine cylinder and piston, acompressor cylinder and piston, said cylinders being connected togetherand said pistons being interconnected to reciprocate as a unit in saidcylinders, an air spring including piston and cylinder elements, one ofwhich is connected to the pistons to move therewith, said air springcausing movement of the pistons on the engine compression stroke, incombination with a fuel injection device for delivering fuel to theengine cylinder including a housing having a bore and an injectionplunger reciprocating in said bore, a passage from said bore to theengine cylinder and an inlet passage for fuel to enter said bore, aspring acting on said plunger to move it in one direction, andpressure-actuated means for moving the plunger in the oppositedirection, said pressure-actuated means being connected to the enginecylinder, said pressure-actuated means including a piston and a cylinderin which the piston reciprocates, said piston being connected to theplunger, and a connection from one side of said piston to the enginecylinder.

10. A free-piston unit including an engine cylinder and piston, acompressor cylinder and piston, said cylinders being connected togetherand said pistons being interconnected to reciprocate as a unit in saidcylinders, an air spring including piston and cylinder elements, one ofwhich is connected to the pistons to move therewith, said air springcausing movement of the pistons on the engine compression stroke, incombination with a fuel injection device 'for delivering fuel to theengine cylinder including a housing having a bore and an injectionplunger reciprocating in said bore, a passage from said bore to theengine cylinder and an inlet passage for fuel to enter said bore, aspring acting on said plunger to move it in one direction, andpressure-actuated means for moving the plunger in the oppositedirection, said pressure-actuated means being connected to the enginecylinder, said pressure-actuated means including a piston and a cylinderin which the piston reciprocates, said piston being connected to theplunger, a connection from one side of said piston to the enginecylinder, and a connection from the other side of said piston to the airspring.

ii. A tree-piston unit including an engine cylinder and piston, acompressor cylinder and piston, said cylinders being connected togetherand said pistons being interconnected to reciprocate as a unit in saidcylinders, an air spring including piston and cylinder elements, one ofwhich is connected to the pistons to move therewith, said air springcausing movement of the pistons on the engine compression stroke, incombination with a fuel injection device for delivering fuel to theengine cylinder including a housing having a bore and an injectionplunger reciprocating in said bore, a passage from said bore to theengine cylinder and an inlet passage for fuel to enter said bore, aspring acting on said plunger to move it in one direction,andpressure-actuated means for moving the plunger in the oppositedirection,

said pressure-actuated means being connected to the engine cylinder,said pressure-actuated means including a piston and a cylinder in whichthe the engine compression stroke, in combination with a fuel injectiondevice for delivering fuel to the engine cylinder including a, housinghaving a bore and an injection plunger reciprocating in said bore, apassage from said bore to the engine cylinder and an inlet passage forfuel to enter said bore, a spring acting on said plunger to move it inone direction, and pressure-actuated means for moving the plunger in theopposite direction, said last means including a piston, a cylinder inwhich said piston reciprocates, and a, valve element substantiallysmaller in area than the piston connected thereto, said valve elementclosing an admission port to the last-mentioned cylinder,

' said spring normally holding the valve element in closed position, andthereby controlling the engine cylinder pressure at which the injectionof fuel occurs.

13. A free-piston unit including an engine cylinder and piston, acompressor cylinder and piston, said cylinders being connected togetherand said pistons being interconnected to reciprocate as a unit in saidcylinders, an air spring including piston and cylinder elements, one ofwhich is connected to the pistons to move therewith, said air springcausing movement of the pistons on the engine compression stroke, incombination with a fuel injection device for delivering fuel to theengine cylinder including a housing having a bore and an injectionplunger reciprocating in said bore, a passage from said bore to theengine cylinder and an inlet passage for fuel to enter said bore, aspring acting on said plunger to move it in one direction andpressure-actuated means for moving the plunger in the oppositedirection, said last means including a piston, a cylinder in which saidpiston reciprocates, and a valve element substantially smaller in areathan the piston connected thereto, said valve element closing anadmission port to the last-mentioned cylinder, said spring normallyholding the valve element in closed position, and thereby controllingthe engine cylinder pressure at which the injection of fuel occurs, andmeans for adjusting the tension of said spring for adjusting thepressure required for causing the injection of fuel.

RALPH J. HOOKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

